1. Field of the Invention
The invention relates to apparatus utilized in the production of hydrocarbons. More particularly, the invention relates to an apparatus and method for preventing erosion of wellbore components utilized in wellbores during production of hydrocarbons.
2. Description of the Background Art
When a wellbore is ready for production of hydrocarbons, wellbore components such as a wellscreen are typically inserted into the wellbore on a string of production tubing. Thereafter production fluid passes through the wellscreen and is pumped to the surface through the tubing. Wellscreen typically includes a perforated inner tube and some type of wire screen (sand screen) therearound to prevent sand and other debris from entering the tubing with the production fluid. The wellscreen, when placed downhole, forms an annular area with the wellbore.
When using a wellscreen in a wellbore, the annular area surrounding the wellscreen is often filled with gravel in a gravel packing operation. FIG. 1 is a cross sectional view of a well including a wellscreen in a wellbore with a gravel pack. Gravel packing is useful for additional filtering the production fluid, establishing a uniform flow of the production fluid along the wellscreen and preventing the collapse of the adjacent formation. FIG. 1 illustrates a formation 100, a wellbore 102 proximate the formation 100, and a casing 104 lining the wellbore 102. A production string 110 with a wellscreen 116 disposed at a lower end thereof provides a path for fluid to pass through the production string 110 to the surface of the well 122 for further processing. Perforations 106 are also formed in the casing 104 to allow production material to flow from the formation 100 into the wellbore 102.
Disposed between the production string 110 and the wellscreen 116 is a cross-over tool 112. The cross-over tool 112 comprises a central pipe 111 and a chute 118 extending outward from the central pipe 111 and into an annular area 114. Gravel 120 is dispensed in a slurry form from the surface of the well 122 and exits at the chute 118 to fill the annulus 114. A wash pipe 108 (shown with dotted lines in FIG. 1) is contained within the production string 110 and serves as a conduit for extracting the liquid from the slurry so that only the gravel 120 remains in the annulus 114.
Gravel packing is not a precise process. For example, some portion of the wellscreen may not always receive adequate gravel packing therearound and may be left exposed. The suction created by the wash pipe as it urges liquid out of the wellbore may compress the gravel, leaving the upper portion of the wellscreen exposed. The gravel may also settle over time, leaving the wellscreen partially exposed. The exposed area of the wellscreen is then subjected to high velocity production fluid containing solid materials. Such solid materials are normally trapped by the gravel thereby prevent damage the wellscreen. However, the exposed portion of the wellscreen provides a path for the solid materials to impact the wellscreen directly, causing premature erosion, corrosion and compromising the structural integrity of the wellscreen.
In response to the erosion and corrosion problems, protective coatings have been applied to the wellscreen. However, the conventional techniques typically require the coating to be sprayed onto wellscreen, which can waste the coating materials and may not adequately cover the entire screen. In addition, the spraying technique does not apply the coating evenly on the wellscreen leaving parts of the wellscreen at least partially exposed to erosion and corrosion. Further, the conventional techniques coat only the screen portion of the wellscreen, leaving the other components, like the interior base pipe, susceptible to erosion.
Therefore, there is a need for a wellscreen that is more erosion and corrosion resistant to impact by fluids containing solid materials. There is also a need for a method of protecting wellscreens from premature erosion and corrosion that can be applied efficiently and evenly and to all parts of the wellscreen for maximum protection.
The present invention generally provides an apparatus and method for preventing erosion and corrosion of wellbore components through the use of a coating applied to the component. In one aspect, the coating includes a metal-based coating and is preferably nickel and phosphorous. The coating may also be an organic-based coating such as phenolic resin containing ceramic or cermet. The coating may be applied to all parts of the wellscreen including the base pipe. In another aspect, a method for fabricating an erosion resistant wellbore component comprises providing the wellbore component and treating the wellbore component with erosion resistant materials. The treating step is conducted by plating the wellbore component, preferably by electroless plating. The treating step may further comprise heat treatment of the wellbore component subsequent to plating.